<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
</head>
<body>
    <script>
        setTimeout(()=>{
            console.log(1); 
        },0)
        Promise.resolve().then(()=>{
            console.log(2);
        })
        Promise.reject().then(()=>{
            console.log(3);
        })
        console.log(4);
        //4 2 1 promise失败，3不输出
    </script>
</body>
</html>